1. Field of the Invention
The present invention relates to a method of forming a stator of an electric rotating machine driven by an internal combustion engine of a vehicle.
2. Description of the Related Art
FIG. 10 is a perspective view showing a conventional stator of an electric rotating machine for vehicle.
In the drawing, a stator 1 includes a stator core 2, a stator winding 3, and an insulator 4. The stator core 2 is cylindrical in shape and is provided with plural long slots 2a at predetermined pitch along the circumferential direction of the stator core 2 in axial direction. The stator winding 3 is wound around the stator core 2, and the insulator 4 is formed into a U-shape to electrically insulate the foregoing stator core 2 and the stator winding 3 from each other.
The stator winding 3 is comprised of one set of three-phase alternating current winding, and a large number of, for example, thirty-six slots 2a are formed for accommodating the stator winding 3.
Manufacturing process of the foregoing conventional stator 1 is now described with reference to FIGS. 11 to 17.
First, a predetermined number of thin strip plates of an SPCC material, which is a magnetic material, are prepared. These plural thin strip plates are then laminated, and outer circumferential portions thereof are welded by laser welding, thus a laminated core 5 formed into a rectangular parallelepiped shown in FIG. 11 being obtained.
A large number of slots 2a are formed on one side in longitudinal direction of the laminated core 5. In the drawing, numeral 5a is a tooth, and numeral 5b is a flange.
A strand 6 composed of a copper wire material that is circular in section and is applied with an insulating coating is wound by a predetermined number of turn of winding in the shape of wave winding at three slot pitch, thus a winding assembly 7A of flat configuration as a whole being prepared. A beginning end and a terminal end of winding the strand 6 forming this winding assembly 7A are used as a lead strand 6a and a neutral point lead strand 6b respectively. Winding another strand 6 additionally forms each of winding assemblies 7B and 7C.
Next, as shown in FIG. 12, the insulator 4 formed into substantially a U-shape is fitted in each slot 2a of the laminated core 5 from the opening side of the slot 2a and is fully accommodated in the slot 2a. The three winding assemblies 7A, 7B and 7C overlap each other staggering by one slot pitch between them as shown in FIG. 13.
The winding assemblies 7A, 7B, and 7C overlapping each other as described above are inserted in the slots 2a every third slot from the opening side of the slots 2a respectively. The winding assemblies 7A, 7B, and 7C are thus mounted on the laminated core 5 as shown in FIG. 15 and FIG. 16.
Subsequently, the foregoing laminated core 5 mounted with the winding assemblies 7A, 7B, and 7C is bent into a cylindrical shape by a forming machine as shown in FIG. 17, and thereafter both end faces of the laminated core 5 are welded together by butt welding, thus a complete stator 1 as shown in FIG. 1 being obtained.
In the conventional stator 1 constructed as described above, the stator winding 3, which is a three-phase alternating-current winding, is obtained by connecting the neutral point lead strands 6b of the strands 6 forming the winding assemblies 7A, 7B, and 7C. Each of these winding assemblies 7A, 7B, and 7C has a phase difference of 120°, corresponding to windings of a-phase, b-phase, and c-phase of the three-phase alternating-current winding respectively.
At the time of mounting this stator 1 on an alternating-current generator for vehicle, the lead strands 6a of the strands 6 forming the winding assemblies 7A, 7B, and 7C are connected to a rectifier.
The conventional stator is constructed as described above, and in the manufacturing process thereof, the winding assemblies 7A, 7B and 7C are inserted from the slot opening side into the insulator 4 after completely inserting the substantially U-shaped insulator 4 in the slot 2a of the laminated core 5.
In the alternating-current generator for vehicle, a very small space is left between the stator 1 and a rotor (not shown), and the insulator 4 interferes with the rotor if the insulator 4 protrudes out of the slot 2a. Therefore, the insulator 4 is formed so that end thereof does not protrude from the opening of the slot toward the inner diameter.
In other words, end of the insulator 4 and end face of a tooth 5b are on the same plane. When inserting the winding assemblies 7A, 7B, and 7C, the end portion of the opening of the insulator 4 does not function as a guide. Hence a problem exists in that it is difficult to insert the winding assemblies making the insertion rather troublesome.
Further, since both sides of the insulator 4 are substantially in parallel, opening side of the slot 4 (2a?) is fully left open under the condition that the winding assemblies 7A, 7B, and 7C are inserted in the slots 2a. Therefore, a further problem exists in that there is a possibility that the strands 6 get out of the slots 2a at the process of bending the laminated core 5, which eventually gives a bad influence on the bending work of the core.
Moreover, due to friction force between the winding assemblies 7A, 7B and 7C and the insulator 4, the end of the insulator 4 is pushed toward the bottom of the slot 2a as the winding assemblies 7A, 7B, and 7C are inserted. As a result, the end face in circumferential direction of the tooth 5b is exposed.
As a result, the end face of the flange 5b rub the wires of the winding assemblies 7A, 7B and 7C, hence a further problem exists in that insulating coating is damaged, moreover, after insertion of the assemblies, there arises any portion where no insulator 4 interposes between the inner wall faces on the opening side of the slots 2a and the strands, which invites deterioration in insulation performance.
The Japanese Patent Publication (unexamined) No. 2000-308314 proposed an attempt for the purpose of improving the insulation performance at the opening portions of the slots described above. Specifically, this Japanese Patent Publication (unexamined) No. 2000-308314 discloses a technique in which a sheet-like insulating member is formed into a tube and inserted in a slot, one end portion of the insulating member is widened, and then a winding assembly is inserted. In this proposed technique, however, several problems exists in that insertion of the sheet-like insulating member and the widening process are troublesome, work efficiency is low, and the work does not go on smoothly.